For me, mid 70s I would consider average. Hi in the 80's. Most important thing about efficiency with all grain is consistency. If you can get the same % everytime....than your recipes and beers will reflect your hard work, and being able to duplicate a previous brew....priceless.

Yeah, I agree that consistency is the most important thing assuming you're up in the 75% range. If you get 75% one batch and 85% the next batch, then it's going to make it impossible to calibrate your recipes.